Embodiments of the invention relate generally to a superhard tip for a rotary machine tool, and more particularly, but not exclusively, for a twist drill or an end mill; to methods for making same and tools comprising same.
Examples of superhard materials are polycrystalline diamond (PCD) material and polycrystalline cubic boron nitride (PCBN) material. PCD material comprises a mass of substantially inter-grown diamond grains and PCBN material comprises cubic boron nitride (cBN) particles within a matrix comprising metal and/or ceramic material. PCD and PCBN may be made by subjecting aggregated masses of diamond grains or cBN grains, respectively, to an ultra-high pressure of at least about 5.5 GPa and temperature of at least about 1,250 degrees centigrade.
U.S. Pat. No. 4,762,445 discloses a composite sintered twist drill that is particularly suited for helically fluted twist drills larger than approximately 3.17 mm in diameter. The hardest material, which may comprise diamond, is located in narrow veins at the leading edges and across the mid line of the drill tip.
There is a need to provide an alternative superhard tip for a rotary machine tool.